Thatcher had media training and put on a voice for television appearances. It was supposed to be her. ‘Caring’ voice - slow and quiet.
The mistake the programme makes is having her use that voice all the time - in her kitchen, meeting the Queen, on the junket to Balmoral. Her normal voice was never heard, just the very affected one for all occasions.
I think Series 4 is the weakest so far. A couple of episodes were duff, and the artistic licence went beyond credible.